The present disclosure relates to stereoscopic image processing technology, and more particularly, to techniques of performing image processing for frame sequential display to alternately display left and right images of a stereoscopic image signal.
3D movies which present different images to the left and right eyes of a viewer, who in turn uses binocular parallax to have stereoscopic impression, have in recent years rapidly become popular. 3D movie theaters have been widespread, and also, 3D movies have been widely viewed in homes using 3D-enabled devices.
Stereoscopic images are typically viewed using liquid crystal shutter glasses in homes. A display device alternately displays left-eye images and right-eye images (frame sequential display), while a viewer wears liquid crystal shutter glasses which block images which would otherwise enter the left or right eye, in synchronization with display. As a result, the viewer perceives left-eye images only using the left eye and right-eye images only using the right eye, and therefore, can have stereoscopic impression due to a parallax between the left and right images.
FIG. 9 shows a scene that a ball moves across a screen. FIG. 10 shows a relationship between positions and times of the ball in images which have been captured at a rate of 60 Hz from each of the left and right points of view in a stereoscopic manner and are alternately displayed for the left and right eyes at a rate of 120 Hz in a frame sequential display scheme.
When stereoscopic images which have been obtained by simultaneously capturing left and right images are displayed in a frame sequential scheme, displayed left and right images are spaced in time by 1/120 sec. It is known that when a human views an object which is moving at an almost constant speed, his or her line of sight moves to follow the motion. FIG. 10 shows, by arrows, movement trajectories of the lines of sight which have followed the displayed ball.
Therefore, as shown in FIG. 11, when an image for one eye is displayed, the position of the line of sight of the other eye has been further shifted, depending on the movement of the ball. For example, when a right-eye image is displayed, the position of the line of sight of the left eye has been further shifted from the position of the ball in the immediately previous left-eye image by an amount corresponding to 0.5 frames. Specifically, when a scene obtained by capturing a horizontally moving ball in a stereoscopic manner is displayed in a frame sequential display scheme, the positions of the lines of sight of the left and right eyes are different from each other in the horizontal direction by an amount (0.5 frames) corresponding to the movement of the ball. The difference in the position in the horizontal direction of the line of sight between the left and right eyes has an influence on the stereoscopic impression of a stereoscopic image, so that the image is perceived as being closer to or further from the viewer than the actual position of the ball is.
Japanese Patent Publication No. 2010-62695 describes a technique of addressing the above problem with the frame sequential display, in which a motion vector is detected from an image signal, an interpolated frame is generated by shifting the phase of an image for one eye by 0.5 frames using the detected motion vector, and stereoscopic display is performed using the interpolated frame.